The present invention relates generally to computer storage systems and, more particularly, to thin-provisioning and copy function in computer storage system.
Storage virtualization technology is widely used. An example is thin provisioning. See, e.g., U.S. Pat. No. 6,823,442. Virtualization technology can improve storage usability and efficiency. The improvement of usability is achieved by concealment of the internal configuration (disk configuration, data location, and so on). The improvement of efficiency is achieved by sharing of the storage resources (disk workload, processor workload, internal bus workload, capacity, and so on). Volume copy technology is also widely used, including, for example, backup, online & batch (for DWH (Data Warehouse), etc.). Examples of copy methods are whole volume copy and copy-on-write snapshot. See, e.g., U.S. Pat. No. 7,716,435.
FIG. 1 shows an example of whole volume copy. When whole volume copy is executed in the case of using thin provisioning technology, a storage administrator has to make thin provisioning pools for primary logical volume (PVOL) and thin provisioning pools for secondary logical volume (SVOL). If a RAID group (RG) has failure, PVOL also has failure. The storage administrator can restore from SVOL. The problem is that it is not efficient to get higher performance. For example, if copied logical volumes are used only for backup, RG #6-8 are used only in the case of backup/restore execution. PVOL #2 may use RG #6-8. It is not easy to provide maintenance because two or more pools are required.
FIG. 2 shows an example of combining thin provisioning pools for PVOL and SVOL. In the example shown, if RG #3 fails, both PVOL #1 and SVOL #1 fail. As a result, it is difficult to combine thin provisioning pools for primary logical volume and secondary logical volume in a storage subsystem because one RAID group failure causes both PVOL failure and SVOL failure. This issue is not recognized by U.S. Pat. Nos. 6,823,442 and 7,716,435.